Gas compression to ultra-high pressures is required in many industrial processes, in the supply of industrial gases for use at ultra-high pressures, and in specialized ultra-high pressure gas storage systems. The compression of gas to pressures above about 100 psig in such applications typically is effected by positive-displacement compressors that utilize solid pistons or diaphragms and require reliable and efficient seals operating at high pressure differentials. Gas compression requires cooling to remove heat of compression, which may be achieved by interstage cooling between multiple stages of compression. Ultra-high pressure compression applications thus may require many stages of compression for efficient operation. Most piston-type compressors require lubrication between the piston and cylinder, and lubricant may be entrained in the compressed gas, thereby requiring efficient oil removal means downstream of the compressor.
Conventional reciprocating positive-displacement compressors may become less efficient as the discharge pressure increases because of the clearance or dead volume required between the moving compressor element (e.g., piston or diaphragm) and the compressor casing. Because of this clearance volume, a small but significant amount of gas remains in the compressor at the end of the compression stroke, and the pressure energy in this gas is lost during the subsequent intake stroke.
These drawbacks of solid-element reciprocating compressors led to the development of liquid piston gas compressors in which a liquid is pumped into a cylinder to compress gas therein by direct contact between the moving liquid and the gas being compressed. After the gas is compressed and discharged from the cylinder, the liquid is withdrawn and another charge of low-pressure gas flows into the cylinder for compression in a subsequent compression step. Many early liquid piston compressors, for example, were designed for air compression service and used water as the compression liquid. Multiple cylinder liquid compressors have been disclosed which provide a more constant flow of compressed gas, and various types of cooling devices mounted in the compressor cylinders have been used.
There is a need in the field of gas compression, particularly in ultra-high-pressure gas compression, for improved compressor systems that avoid the drawbacks described above for solid-element reciprocating compressors. In particular, there is a need in the industrial gas industry for improved compression systems to provide ultra-high-pressure gas products and for ultra-high-pressure gas storage systems.